Transmission regulating system



' Aug, 3o, 1932.

y c. s. DEMAREs'r TRANSMI S S ION REGULATING SYSTEM Filed Nov. 10. 1951 INVENToR C. en/mest BY ATTORNEY Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE CHARLES S. DEMAREST, F RIDGEWOOD, NEW JERSEY, ASSIGNOR TO AMERICAN 4TELE- PHONE .AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TRANSMISSION BEGULATING SYSTEM Application filed November 10, 1931. Serial No. 574,207.

This invention relates to transmission systems and more particularly to means for regulating transmission on the lines of such systems.

In telephone or telegraph transmission systems, particularly of the carrier type, it may be desirable to automatically regulate the transmission over lines of such systems so that the current at the end of the line will be of constant output or of an output between desired levels. This has been accomplished by transmitting a pilot channel over a line and utilizing increases or decreases in said pilot channel to cut in or out of the line elements of networks or artificial lines to regulate. transmission to keep the output between desired levels. The means for switching in and out of the line the elements of these networks have heretofore been relays. In such systems, particularly those utilizing a number of carrier channels, it is necessary to effect very dependable operation of these relays as their contacts may be directly in the transmission circuit. Accordingly, careful attention to their mechanical adjustment has been necessary. The arrangements of the invention provide a means for automatically controlling the transmission in a line by means of a pilot 'channel without the use of relays and hence afford 'the particular advantage of providing a device which eliminates mechanical moving parts in such a system.

In the arrangements of the invention the pilot channel is transmitted through the variable network or artificialline to the rey-such that the number of elements'of 'the artificial line to be cut intothe circuit will be dependent upon the voltage of the received current. Other objects and features of the invention will appear more fully'from the detailed description thereof" hereinafter given.

The invention may be more fully understood from the following description together with the accompanying'drawing in the figure of which is shown a circuit diagram illustrating a preferred embodiment `of the invention.

In the drawing is shown a transmission line L in which it may be automatically desired to regulate transmission by means, for example, of a pilot channel transmitted over the line. Accordingly, there would be includedin the line L a plurality'of artificial lines or networks, such as N1 and'Ng.` Each4 of these would comprise series and shunt elements. In the network N1 would be kthe series resistance elements 1 and the shunt element comprising the circuit;2 including elements of resistance and inductance. Y In the network N 2 would be the series resistance elements 3 and the shunt element comprising circuit 4vincluding 'elements of resistance and inductance. Networks of this type are well known in the art. the line of the elements of network; N1 is controlled by a switching device comprising the gas-filled thermionic tubes 5 and 6. The

, connection in the line of the elements of network N2 is controlled by a switchingl device ,so

comprising the 7 and 8.

The gas-filled thermionic tubes 5, 6, 7 and 8 are such that when the input voltage apgas-filled thermionic tubes plied to the grid is of a certain value the tube..

will operate and an arc of relatively low resistance will be formed between the cathode and plate of the tube. Obviously when the tubes are in a non-operative condition and no low resistance arc exists, the resistance between cathode and plate is very high; The

The connection in tube 5 comprises a cathode 9, a heating ele'- ment 10 for the cathode, a grid 11, and a plate 12. The grid circuit'would include the resistance 13.. The cathode-plate circuit would 5 include theV current limiting resistance 14, v a battery 16,V the inductance 17, and the rev betweenithe cathode and plate'.A YThe resistance of this arc would be so low that itwould in effect close the following-circuit'about the Y series elements 1 of .network N1,from,the

tip side of line L, conductor '19, cathode- .Lti-piside. .of VlnefL. Accordingly, series-.ele- ...ment h1 ofinetwork N1 will not be connected ...in the-line. 'lhegasflilled tube- 6` comprises "25.-faccathode 23,..a .heatingffelement 24for the.

cathode, a grid 25, and a plate 26. .The

Y ,plate circuitncludesthe current limiting` .resistance Vr27, the winding-of transformer ..28,. the. battery.V 29, inductance 30,: and wind- 93 .ingottransformera. .The-inputcircuit is` connected L, through a AVtransformer 22 .to a potentiometer 21 and thence to acircu1t20 bridged .across the line-L. When `nol'pilot .,channelfcurrentfis owinglin line L. and cir- ,..cuit.2O,1there.-Will be no. input voltage .applied .150. theggrild-.,of..tube.6 ,and it; will not be operoated. .Hencea highy resistance will exist. be-

` YLtween,the.cathodeand plate of the tube.v .The

sshunt circuit element2k across lineL iscom- 'o 4. pleted by .conductors 32 and 33 .across the .f-liighresistance;between the cathode and plate .ofztube -6..an`d hencetheshunt element of .net-,work Nl .is. not connected in the.. line. .-L.

. {Accordingly-when. n-ofpilotchannel is trans- 145 .mtted overlinerL. thenetwork N1 will not .lberconnected infthe line. l

'..Thegas-lfilled. tubes 7. .and -8and theirv cir- .cuits ...are lsubstantially asimilar to thoseof series element ofnetworlr.N2 maybe disl .,connectedfrom lineL. Tube 8 has itsfinput V.circuit connected .through a potentiometer 37 t0 the circuit 36 which is connected by @transformera .to..the line L. fWhen no invput .voltage .isappliedtoltube 8 fit .will not etween -the. cathode andA plate. l This high :resistance will` be includedby yconductors 41 and in the path ofshunt circuit. element .4 acioss .theQline L. ...Jfi'ccordingly,` the shunt .elementtf networleN2 may.bejdisconnectedy Y 5 lromllneL.

`.tubes..and 6,.=r.espective`ly. Y.Normally tube. :7 is: operated anda,lowresistance .arc exists` Lbetween its :cathode and .plate. With zthis y flow resstanceand Aconductors 438 and .39 the .,:bef operatedT anda. high, resistanceY will exist gli b lf it is desired to regulate transmission in the line L, a pilot channel frequency will be transmitted thereover and the voltage there-- from will be applied over circuit 2O to the input of tubeV 6. If the Vvoltage across the input of tube 6 should rise to a value sufficient to operate the tube, an arc will be established from the Vcathode to the plate inthis tube. This' arc will be an intermittent one as itwill be intermittently l .quenched by the alternating current applied .to rthe pla-te circuit yfrom source 31. However, Vthe formation of this intermittent arc between the cathode and plate of tube 6 will -.so'1re'duce2 the resistance between these elev:mentsas'toeectivelyv close the. shunt element of network N1.' At the saine time this intermittent `Vreduction `of the resistance in the plate circuit of tube 6 would furnish a low resistance path'for the alternating current from'source 31 through-thepriniary wind- .ingoftransfornier 34. g rThis currentwould .iberectified by device 57 and be applied in sucient strength to resistance 58 to reduce the volta-ge on. the plate of tube 5 so that i Y .1 y

the arc.there1nwnl be quenched. The condenser ..59 shunted across resistance 58 1s so proportioned 4as Vto maintain a continuous .iow .offcurrent of sucient magnitude through'resistance58 tolieep the arc in tube l5zextingui'shed. This .would change the low resistance arc eristingintube5 to a condi` tionof noarc at all. vThis'would eectively removethevlow. resistance between the cathode and plate of this tube andsubstitute .therefor a high resistance. This would open .the normal shunt path. across .the series ele- .nient l.V of .the ,network Nl. As has been gpointed but .the alternatingV current from .source..31in'theplate circuit of tube 6 will :noti permanently quench the are in this cir- .cuitas long asv it is continuously reestablished-by the applicationV of sufficient alternating voltage to the grid from the input circuit, and. as a resultfthe shunt element 2 is effectively shunted across line L. The alter- .nating quenching frequency fronisource 31 .should preferably be high as compared to the .frequency-orfrequencies `regulated by the 'networki 1 l. Accordingly, it will be seen l that the` operation of tube 6 will cause the tube 51. tobe deenergized, and whenv the tube r6 is deenergized tube 5 will again be operated.

.The removal of the short circuit on series elementl permits voltageto be applied through Atransformer 35 and circuit k'36 to the input of tube S-.andif sufficient pilot channel voltage -isreceived .withNl in circuit tubes 7 and 8 will function.

received current is above the desired amount, sufficient voltagewlll be received at the input 'of tube 6 to. operate this tube andto deenerq .gizetube.5. This willconnect the network .An illustration of the generai operation of the..arrangement shown lis as follows: If the N1 into the line L and reduce the volume transmitted over the line. If the received current had been below the desired amount the switching device comprising tubes 5 and 6 would not have been operated and the network N1 would not have been connected into the line. If, after the network Nl has been connected into the line in the manner described, the pilot or control current flowing in the series element l of the network N1 produces sufiicient voltage on the grid of tube 8, the tube 8 will operate and the tube 7 will be released. The switching unit comprising tubes 7 and 8 will then function to cut the network Ng into the transmission line L and further reduce the volume transmitted thereover. By means of a circuit such as 43, additional switching arrangements and additional networks might "be connected into the line L. Accordingly, successive networks may be connected into the circuit in a manner similar to that heretofore described until the received Current is reduced to the desired value. It might be desirable in utilizing the arrangements shown to have half of the networks connected on normal current and half disconnected so that the range of adjustment above and below the normal value would be equal. In the arrangement shown, it may be assumed that all of the networks are approximately of equal value so that their operation in sequence will increase the loss in the line in equal steps. Such an arrangement would be best suited to uses in cases where a large number of steps would not be required. It' large attenuation, however, is required in the variable artificial line and at the same time it is necessary to have this change occur in small steps, a variety of sizes of networks might be utilized.

In the arrangements of the invention sufficient amplification will be obtained from the gas-filled tubes of the kind indicated to permit operating directly from the currents received from the transmission circuit without requiring a receiving amplifier particularly for the purposes of raising these currents to the necessary level for the control device. Gas-filled tubes of the type described also have the characteristic of being critically responsive to the specific value of the applied input voltage so that they can be adjusted to operate at the desired value of receiving current. These features constitute l further advantages of the arrangements of the invention over relay devices for the particular apparatus proposed in transmission regulating systems.

While the arrangements described might be particularly adapted to a carrier current transmission regulating system, the principles employed would also apply to a control current system either for voice currents or radio circuits. Accordingly, while the invention has been described as embodied in certain s ecific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied Vforms without departing from the spirit of(k the invention as defined by the appended claims.

What is claimed is:

l.' A transmission line, a network comprising an element in series in said line and an element in shunt in said line, two gas filledV Y thermionic tubes, means for completing the circuit for said shunt element over the cathode-plate circuit of a normally inoperative one of said gas filled thermionic tubes, a shortl Y circuit about said series element completed an element in shunt in Said line, means forv completing the circuit for said shunt element over the cathode-plate circuit of a normally inoperative gas filled thermionic tube, a short circuit about said series elementcompleted over the cathode-plate circuit of a normally operated gas filled thermionic tube, means controlled by the operation of said first tube for releasing said second tube, means controlled by the voltage of currents transmitted over said line for operating said first tube, a second network similar to said first network, a combination of gas filled thermionic tubes similar to said first mentioned combination of tubes for effectively connecting the elements of said second network into said line, and means controlled by the voltage of currents transmitted through said first network for controlling the operation of said second combination of gas filled tubes.

3. A transmission line, a network comprising an element in series in said line and an element in shunt in said line, means for completing the circuit for said shunt element over the cathode-plate circuit of al normally inoperative gas filled thermionic tube, a short circuit across said series element completed over the cathode-plate circuit of a normally operated gas filled thermionic tube, means controlled by the operation of said first tube for releasing said second tube, means controlled by the voltage of currents transmitted over said line for operating said first tube, additional networks controlled by additional combinations of gas filled tubes similar to said first network and combination of tubes, and means for successively connecting said networks into said line by operating each combination of tubes by the voltage of currents transmitting through the preceding network.

4;. A transmission line, a network compris;

ing an element in series in said line and an element in shunt in'said line, means for complet.- ringthe circuit for said shunt element over the 1 .5 cathode-plate circuit of `a. normally inoperative gas filled thermonic tube7 a Short circuit about said series element completed over the cathode-plate ercuit'of anormally operated Y.

gas filled thermiono tubefmeans controlled lorby the operation of said first tube orreleas-V ing said second tube, means controlled bythe voltage of currents transmitted over said line for-operatingsaid'rst tube,'and mea-ns 0perative when the input Voltage applied to said 15 first tube ceases vfor releasing said irst tube and causing sa-idsecondto become operative again. Y Y

Y 5. A transmission line, a. network comprising an element in series in said line rand an 20 element in shunt in said line, two gas filled thermionio tubes, means for Completing the Circuit for said shunt element over the cathode-plate circuit of one of said tubes, a short oireuitabout Said series element Completed ,5 over the cathode-plate circuit of the other of said tubes, and means Controlled by the voltage of Currents transmitted over said line for controlling the energization and deenergiza-- tion ott said gas lled tubes. Y 30 In testimony whereof, I have signed my name to this specification this 9th day of November 1931. l

Y CHARLES Si DEMAREST. 

